In manufacturing a semiconductor device, a fine circuit pattern is formed on the surface of a semiconductor wafer. Conventionally, such a circuit pattern has been formed by a photolithography process. More specifically, a resist film is formed on the wafer. This resist film is exposed to light through a photomask, and then developed. Thus, the pattern formed on the photomask is transferred to the resist film to form a resist pattern. This resist pattern is used as a mask to process the wafer, thereby forming a circuit pattern.
The cost related to the exposure apparatus used in such a photolithography process significantly increases with the miniaturization of the circuit pattern. One reason for this is that the cost of the exposure apparatus itself exponentially increases. In addition, various contrivances are needed in the photomask to obtain resolution comparable to the wavelength of light used. Thus, the cost of the photomask is also rapidly increasing.
As a pattern formation technique to solve this problem, the nanoimprint lithography has been proposed. In the nanoimprint lithography, a pattern to be formed on a wafer is formed beforehand on a template. The template is pressed against a liquid resin material dropped on the wafer. With the template pressed, the resin material is cured. Thus, the pattern made of the resin material is formed (see, e.g., JP-A 2008-194980 (Kokai)). That is, the nanoimprint lithography is a one-to-one transfer technique. Here, the pattern on the template is typically formed by performing EB writing and etching on a template substrate.
The aforementioned nanoimprint lithography is broadly divided into a thermal nanoimprint lithography and an UV-nanoimprint lithography. In the thermal nanoimprint lithography, a resin material is melted by heating. A template is pressed against the melted resin material. Then, the resin material is cured by cooling. On the other hand, in the UV-nanoimprint lithography, a transparent template made of e.g. glass is pressed against a liquid photocurable resin material. Then, this resin material is cured by ultraviolet irradiation.
In the nanoimprint lithography, even in the state of the template pressed against the resin material, the resin material remains between the protrusion of the template and the wafer. The thickness of the layer of this remaining resin material (residual layer) is referred to as residual layer thickness (RLT). The residual layer thickness depends on various conditions, such as the amount of unevenness of the pattern formed on the template, the amount and location of the resist material dropped on the wafer, and the spread state of the resin material pressed by the template. In other words, the residual layer thickness is determined by circumstances. However, the problem is that variation in the residual layer thickness involves variation in the condition for subsequent processing on the wafer. This makes it difficult to perform accurate processing on the wafer.